Peters, Pamela
Wm.C. Brown Pub., 1993
Buku Referensi
American Society of Civil Engineers, 1987
Buku Referensi
Whitfield, John
EPA Press, 1995
Buku Referensi
edited by A.D. Austen, R.H. Neale
International Labour Office, 1995
Buku Referensi
Liggett, John V.
Prentice-Hall, 1993
Buku Teks